In general, a belt conveyer system is provided with a device that prevents deviation of the belt in the axial direction of end rollers to which the belt is entrained. In particular, as for a curved conveyor, two end rollers are separated at a predetermined angle and a belt is entrained about these end rollers. Therefore, the belt is stretched into a fan shape and a centripetal force toward the center of the fan shape acts on the belt during operation. Consequently, the curved belt requires positional retention of its outer periphery in order to prevent positional deviation.
As for a belt retention guide for preventing deviation of a belt, there is known a device that pinches beads attached along the peripheral edge of the curved belt, with a pair of rollers fixed on the body of the conveyor. The curved belt is driven in the circumferential direction without allowing displacement in the radial direction by a plurality of such belt retention guides along the peripheral edge of the curved belt.